Study shows CWD prions viable in muscle tissue

By Linda Bell
Correspondent

A research study described in January on NewScientist.com, a news service of "Science Magazine," established that chronic wasting disease prions from deer and elk can be found in the skeletal muscle tissue of infected animals.

It has long been thought that CWD prions mainly concentrated in the brain, eyes, spinal cord, lymph nodes, tonsils, pancreas and spleen. The recent study, however, demonstrates that humans consuming or handling meat from CWD-infected deer are at risk to prion exposure.

CWD is similar in behavior to bovine spongiform encephalopathy, known as BSE or mad cow disease. So far, no data proves conclusively that CWD has been transmitted to humans. (See November 2005 North Forty News, "Chronic wasting disease discovered in wild moose.") The Colorado Division of Wildlife, however, advises hunters to not consume any meat from animals known to be infected with CWD.

Michael Miller of the Colorado Division of Wildlife and Edward Hoover, lead scientist at the Prion Research Laboratory at Colorado State University's College of Veterinary Medicine and Biomedical Sciences, are two of the seven researchers who authored the study showing how CWD could be introduced in transgenic mice through prions in muscle tissue.

According to NewScientist.com, the research team replaced the gene for a normal mouse version of the prion protein with the normal gene from deer, so the mice produced normal, healthy deer protein.

Using two control groups, the researchers injected the mouse brains with either extracts of leg muscle or tissue from the central nervous system from infected deer. A year to 18 months later, all the mice developed encephalopathy. Muscle tissue took slightly longer to cause the disease than brain tissue, demonstrating it had slightly less prion, according to the study.

A control group of mice injected with healthy deer tissue free of CWD showed no signs of the disease.

Meanwhile, CWD keeps spreading throughout the United States as well as overseas within captive herds. The Kansas Department of Wildlife and Parks confirmed in January the state's first occurrence of the disease in wild deer.